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arXiv 0901.2046astro-ph.GA
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静止坐标系UV与使用Sersic轮廓拟合的星系光学形态:形态学K-校正的重要性

Rest-frame UV versus optical morphologies of galaxies using Sersic profile fitting: the importance of morphological K-correction

Abhishek Rawat, Yogesh Wadadekar, Duilia De Mello

摘要:

我们显示了一个样本的162个中间红移(中位数红移1.02)星系的休息帧的UV形态与他们的休息帧光学形态的比较。我们从哈勃太空望远镜(HST)使用WFPC 2(F300 W)获得的最深的近紫外图像中选择样本,作为哈勃超深场活动与HST/ACS GOODS数据集重叠的平行观测的一部分。我们在WFPC 2/F300 W中执行单组件Sersic配合(静止帧UV)和ACS/F850 LP(静止帧光学)带,并推断Sersic指数$n$被估计为在静止帧UV中比静止帧光学更小,导致合并候选人的数量比其他人高估了约40-100%-取决于用于识别合并候选者的$n$中的截止。这种效应似乎是由n(F300 W)<= 0.5的星系所主导,而n(F850 LP)的值约为1.0。我们认为,这些对象可能是星团恒星形成星系或较小的合并,这两个基本上是污染物,如果一个有兴趣确定主要的合并。此外,我们还发现,轴比b/a是较低的证据,即椭圆率(1-b/a)是更高的静止帧UV相比,静止帧光学。此外,我们发现,在静止坐标系UV,高椭圆率(e >= 0.8)对象的数量是高的一个因素的~2.8相比,静止坐标系光学。这表明,高z LBG中细长形态的报告优势可能只是与高z研究中使用静止帧UV数据集相关的偏差。

英文摘要:

We show a comparison of the rest-frame UV morphologies of a sample of 162 intermediate redshift (median redshift 1.02) galaxies with their rest-frame optical morphologies. We select our sample from the deepest near-UV image obtained with the Hubble Space Telescope (HST) using the WFPC2 (F300W) as part of the parallel observations of the Hubble Ultra Deep Field campaign overlapping with the HST/ACS GOODS dataset. We perform single component Sersic fits in both WFPC2/F300W (rest-frame UV) and ACS/F850LP (rest-frame optical) bands and deduce that the Sersic index $n$ is estimated to be smaller in the rest-frame UV compared to the rest-frame optical, leading to an overestimation of the number of merger candidates by ~40-100% compared to the rest-frame optical depending upon the cutoff in $n$ employed for identifying merger candidates. This effect seems to be dominated by galaxies with low values of n(F300W) <= 0.5 that have a value of n(F850LP) ~ 1.0. We argue that these objects are probably clumpy starforming galaxies or minor mergers, both of which are essentially contaminants, if one is interested in identifying major mergers. In addition we also find evidence that the axis ratio b/a is lower, i.e. ellipticity (1-b/a) is higher in rest-frame UV compared to the rest-frame optical. Moreover, we find that in the rest-frame UV, the number of high ellipticity (e >= 0.8) objects are higher by a factor of ~2.8 compared to the rest-frame optical. This indicates that the reported dominance of elongated morphologies among high-z LBGs might just be a bias related to the use of rest-frame UV datasets in high-z studies.

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